Coupling device



July 14, 1936. R DE TAR 7 2,047,360

COUPLING-DEVICE Filed July 6, 1932 ELEEEm IN VENTOE DonaZzZlRDeT a1;

HIS ATTO/E'NEK Patented July 14, 1936 UNITED STATES PATENT OFFICE COUPLING DEVICE of Delaware Application July -6, 1932, Serial No. 521,002

6 Claims.

My invention relates to coupling devices and, more particularly, :to shielded inter-tube transformers of the'types utilized in radio receivers.

An inter-tubecoupling device of the type to which my invention pertains comprises aplurality of transformer windings, a plurality of variable tuning condensers, means for supporting the windings and .condensers in close proximity to one another and shielding means for preventing the magnetic field-of the transformer from influencing :adjacent apparatus in a receiver. Not all such devices, however, constructed according to the teaching of the art prior to my invention, lend themselves to simplified manufacturing processes and many of them are so constructed as to preclude accurate tuning and adjusting-subsequent to assembly into radio receivers Furthermore, the prior art devices referred to are prone to lose their adjustment in use'and, in general, are not constructed with sufficient rigidity as to prevent injury during shipment of receiversin which they are mounted.

It is, accordingly, an object of my invention to provide an improved inter-tube coupling device.

Another object of my invention is :to provide an inter-tube coupling device'that shall be simple in construction and shall lend itself readily to mass production.

Another object of my invention :is to provide a coupling device of such .rugged construction that its adjustment is not likely to change during use.

Another object of my invention is to provide a coupling device :all parts of which shall be readily accessible for adjustment after assembly into a radio receiver.

An inter-tube coupling device constructed according 1170 my invention preferably comprises a cylindrical shield of non-magnetic metal, such as copper, wherein is mounted a tunable transformer assembly. The shield is constituted by separable cap and can portions, threadedly engaged with each other, and the-transformer windings, as well as the tuning condensers therefor, are supported within the shield by a mounting bracket that depends fromthe cap portion. Each of the tuning condensers is adjustable, the cap portion of the shield being provided with openings to permit the insertion of an adjusting device such, for example, as a screw-driver.

Additional details of my improved coupling device will hereinafter be referred to specifically.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself,

however, both as to its organization and its method of operation, together with additional objects and advantagesthereof, will best be understood from the accompanying drawing, wherein 5 Figure 1 is an exploded view in perspective of a coupling device constructed according to my invention;

Fig. 2 is a sectional view of the device taken along a line corresponding to the line 2-2 in 10 Fig. 1;

Figs. 3 and 4 are cross-sectional views of modified forms of coil supports; and

'Fig. 5 is an exploded view of a condenser assembly.

Referring to Figs. 1 and 2 of the drawing, a plurality of transformercoils I and 3 are threaded .onto a wooden rod 5 which is held between the depending ends of a U-shape supporting bracket 1. The rod may be affixed to the said depending 2O ends by tacks 9. It may be hollowand supported by the engagement therewith of ofiset portions l l of the ends, as shown in Figure 3 or, still further, asshown in :Figure 4, bymilled bolts 13 and I5 or the like.

The supporting bracket is spot-welded, as indicated at H, to the interior surface of the top of a circular metallic cap 19, the edge of which is screw-threaded to receive a shielding can 2|.

A plurality of threaded bolts 23 extend up- 30 wardly through the supporting bracket, and the cap, in order that the coupling device may be mounted in place belowa shelf 25 in a radio receiver chassis, as shown in the drawing, or in any other desired position. Preferably, the bolts are 35 spot welded to the bracket before the latter is welded to the cap.

Also suspended from the U-shape supporting member, as by a plurality of small screws 27, is a panel member or plate 29 of insulating material. 40 The said panel member is made, preferably, of porcelain or the like, which has been treated with linseed 'oil to prevent the occlusion of moisture in its surface pores. The panelmember is generally circular .in configuration, and :the periph- 45 ery thereof is provided with a plurality of small indentations or bays 3| to accommodate leads 33 which extend to the exterior of the device through a plurality of openings 35 in the cap member in alignment :therewith.

'The cap is provided with a shoulder 36 to permit egress of the leads 33, or it maybe provided with a beveled end .for the same purpose.

It :might also be mentioned, .in passing, that the wooden'rod 5=on which the transformer wind- 55 ings are mounted is, preferably, pre-treated to prevent the absorption of moisture, by boiling in ceresin wax,

The function of the panel member 29 is to serve as an insulating support for a. plurality of variable tuning condensers, 3i and 39, which condensers, respectively, are connected in shunt to the transformer windings I and 3. Inasmuch as these tuning condensers may be alike insofar as the number of plates is concerned, though not necessarily identical, corresponding parts thereof have been similarly designated in the drawing, and a description of the tuning condenser 3'7 is sufiicient.

The tuning condenser 3?, which is more clearly shown in Figure 5, is constituted by two thin metallic plates ll and Q3, and two relatively thick metallic plates 45 and ll. The plates ii and at are conductively connected together, and the plates 33 and M are also in conductive contact with each other. The two groups of plates are disposed at right angles to each other, with the plates inter-leaved. Thin sheets of mica 49 are interposed between the plates to prevent the plates of one pair from making contact with the plates of the other pair.

The thick member of each pair of plates is provided with a plurality of soldering lugs, to one of which is connected the terminal of the associated transformer winding, and to the other of which is connected one of the leads 53. One pair of plates is firmly held to the insulating panel 29 by a plurality of rivets 5i extending therethrough. Of the two plates constituting the other pair, the plate fill nearest the panel is held thereto by a. hollow rivet 53 at one end and, at the other end, by a similar hollow rivet 55 which extends through it and the outside plate 35. The outside or thick plate 55 is spaced from the inner plate by a small washer 57, which encircles the rivet 55 in order that space may be provided for the accommodation of the plate Al.

The outside plate i-5 is so shaped that it tends to curve outward, away from the riveted end. The end thereof farthest from the riveted end is provided with an offset portion 58 which, when the plate is not under tension, is substantially parallel to the insulating base plate.

For adjustment purposes, a screw 59 extends through the hollow rivet 53 which holds the bottom plate All against the insulating panel 29 and, after passing through the parallel offset portion 58 of the bendable condenser plate 45, threadedly engages a rocking nut 5!, one face of which is provided with a plurality of extensions 63, and the periphery of which is provided with a plurality of bevelled surfaces 65 which merge into the said extensions. As will be noted from an inspection of Figure 5 of the drawing, the opening in the free end 53 of the movable condenser plate 65 has such a configuration that it accommodates the extensions of the rocking nut, thus preventing the said nut from turning when the screw is turned.

Since the bevelled faces of the rocking nut permit the said nut to adjust itself to different positions of the free end of the movable plate, the screw head is permitted, at all times, to be properly centered in the hollow rivet 53, thus rendering the adjustment more stable.

I also find it expedient, though not obligatory, to interpose' a copper shielding element between the two transformer windings, in order to provide means for adjusting the coupling therebetween to the proper value. As shown in the drawing, the shield may take the form of a copper ring 81 having a central, axially offset, circular flange 69 which engages the wooden rod 5, on which the coils are mounted, with suflicient friction to hold it in adjusted position.

It is customary to mount inter-coupling units, of the type to which my invention pertains, in a depending position beneath a metallic shelf, or an equivalent element, in a radio receiver. Also, as is well known to those skilled in the art, the tuning of such an inter-tube coupling unit is influenced by the inter-electrode capacity of the tubes to which the transformer windings are connected and other stray capacities in the receiver. Obviously, therefore, some slight readjustment of the tuning of the device is necessary after it has been installed in a radio chassis. To this end, therefore, I provide the openings 34 in the cap member in alignment with the adjusting screws 59 of the variable condensers and also provide a plurality of aligned openings in the shelf member or the like, to which the device is affixed by means of the mounting screws 23. Such being the case, it is clear that, through the use of a small screw-driver, preferably one of the type having a shaft of bakelite or the like, the tuning condenser may be accurately adjusted during the testing and lining up of the receiver.

Furthermore, since the can may be unscrewed from the cap member, and thus removed, readjustment of the coupling between the coils is also possible after the device is assembled into a receiver.

In certain instances, it may be desirable to broaden the tuning of one of the circuits of the transformer. The broadening may, of course, be accomplished by effectively adding resistance to the circuit and, specifically, such resistance may be added by inserting an iron plug in the end of the coil form, such as the plug i5 shown in Figure 4,, instead of the brass or copper plug hereinabove referred to. Through variation in the length and diameter of the iron plug, the losses, and thereby the broadness of the tuning, can be varied. Obviously, it also lies within the scope of my invention to make use of two iron plugs, if desired.

From the foregoing description of a coupling device constructed according to my invention, it will be apparent that I have achieved improvement in many of the details thereof, the net result of which is a. device that is distinctly a step forward over devices of the prior art. Perhaps the best exemplification of such prior art devices may be found in the copending application of G. L. Beers, Serial No. 270,285, filed 4-16-28, and assigned to the Westinghouse Electric and Manufacturing Company. It is not necessary to refer to the Beers coupling unit in detail, but I wish to make it clear that my improved coupling device is an improvement thereover in the following respects, among others:

(l) The condenser units are mounted in parallel relationship upon one surface of the insulating base plate. This makes it possible to thorougly insulate the primary and secondary circuits from each other. In substantially all prior art devices, including that disclosed in the Beers application, the primary circuit is connected to the secondary circuit, and the tuning condensers are mounted on opposite surfaces of the insulating base plate.

(2). The condensers and coils are mounted in a cap member by means of a single U-shape bracket, which supports the coil form at its end, supports also the insulating capacitor mounting panel at intermediate points, and holds the screws for mounting the coupling unit at its center portion. In previous designs, two separate brackets for the coil were necessary and tabs bent out of the shield can were utilized for holding the condenser mounting plate. My improved device is much more rigid, therefore, and is also easier to service.

(3) Complete shielding of the transformer is accomplished by providing a fixed cap member into which the shield can is threaded. The shield, therefore, is removable and testing and servicing are thereby greatly facilitated. Furthermore, the shielding is much more complete than is obtained in devices constructed according to the prior art, by reason of the fact that the can makes intimate contact with the cap.

(4) The cap, as shown in the drawing, has an offset portion which is threaded. This ofiset portion is provided with openings to accommodate leads extending from the transformer windings. This results in a less expensive device than those constructed previous to my invention, since openings in the sides of the shield proper are eliminated. It also makes possible the removal of the shield, without interference with the connecting leads.

(5) In coupling devices constructed prior to my invention, the spring plates of the variable condensers are offset at the fixed ends thereof to compensate for the thickness of the fixed plate. Such an offset is difficult to accurately control in mass production, and is obviated by the use of the spacing washer in my improved device, with the result that a more uniform prodnot is obtained.

(5) The rocking nut, through which the capacitor adjusting screw extends, is a fairly important feature of my invention. Through the use of such a nut, the screW head is permitted to center itself in the hollow rivet through which it extends, irrespective of the adjusted position of the bendable condenser plate, with the result that the adjustment, once having been obtained, is relatively stable.

In addition to the advantages of my improved device enumerated above, other advantages will be at once apparent to those skilled in the art to which my invention pertains. Furthermore, many modifications of my invention will at once be suggested to such persons and many specific embodiments will be apparent. My invention, therefore, is not to be limited except insofar as is necessitated by the prior art, and by the spirit of the appended claims.

I claim as my invention:

1. An inter-tube coupling device including a shield having a cap portion, reactors supported from said cap portion, and means for aflixing said cap portion against a support, the said cap portion being provided with a shoulder having a plurality of openings therethrough to accommodate leads extending from the interior of the shield and providing a supporting surface in such spaced relation thereto as to permit the egress of said leads between said shoulder and the said support.

2. In an inter-tube coupling device, an air core transformer, means connected with one of the windings of the transformer for tuning said winding, means for altering the inductance of at least one of the windings of the transformer without appreciably affecting the inductance of another winding, and a metallic ring movable along the core of the transformer between two of the windings for adjusting the coupling therebetween.

3. An inter-tube coupling device including a U-shape bracket, a condenser mounting plate supported from said bracket, a transformer mounting core supported between the ends of said bracket, said core being of non-magnetic material, means carried by said bracket and projecting into the core of the transformer for changing the inductance of the transformer winding, a pair of tuning condensers mounted in parallel relation to each other on the same face of said mounting plate, and a shield for said device comprising separable parts providing a shallow base and a deep cover member having a screw thread connection whereby a positive electrical connection is provided between said separable parts.

4. An inter-tube device including, in combination, a shield constituted by a plurality of metallic elements including a cap element and a can element threadedly connected together, an air core transformer mounted in said shield and including a core, a U-shaped supporting bracket mounted on the cap element, and having ends extending therefrom in a direction to enter the can element, means for supporting said core between the ends of said bracket, an insulating plate supported by said bracket intermediate and in spaced relation to said core and the bottom portion of said bracket, and tuning means for one of the windings of the transformer connected with said winding and mounted on said plate.

5. An inter-tube coupling device for radio receiving apparatus and the like, including in combination a transformer having a non-magnetic core, mounting means for the transformer including metallic elements inserted in the core for controlling the inductance of a transformer winding, an insulating base plate carried by said mounting means adjacent to said transformer and a pair of tuning condensers mounted on a single face of said plate in parallel spaced relation to each other.

6. An inter-tube coupling device for radio receiving apparatus and the like comprising a transformer having a non-magnetic core and at least two spaced windings thereon, tuning means for the transformer and an insulating mounting plate for said tuning means, said last named means being mounted thereon in spaced parallel relation and on a single surface thereof, a U- shaped metallic bracket arranged to support said plate and said core including supporting means connecting the core and the bracket and adapted to adjust the inductance of at least one of the windings of the transformer.

DONALD R. DE TAR. 

